1. Field of Invention
The present invention is directed to a sliding gate valve having particular application for use as a furnace valve in which the pouring orifice is substantially horizontal. The invention is also directed to the method of operating the valve to close in the up position of the slide gate. Also the invention is directed to remanufacturable sliding gate members and top plate members.
2. Summary of the Prior Art
The prior art is exemplified by Shapland U.S. Pat. No. 4,063,668 issued December 1977 and also patents of Metacon A. G. U.S. Pat. Nos. 4,269,399 and 4,273,315.
As to the Shapland U.S. Pat. No. 4,063,668 it should be noted that it utilizes bilaterally symmetrical slide gates and top plates. While the use on a bottom pour vessel such as a ladle, where there is substantial clearance, has been highly satisfactory; when employed on the side of a furnace where extensive auxiliary equipment appears, space limitations can cause a problem.
Moreover, in the application of sliding gate valves of the aforementioned type, a particular undesirable wear phenomenon occurs. Specifically, it has been found that a depression pocket is generated by erosion forces in the wall of the opening through the fixed plate adjacent its sliding surface and limited to the region thereof that faces the direction of movement of the slide gate upon valve closure. Continued cycling of the valve by moving the slide gate between its open and closed positions increases the effects of these erosion forces causing an enlargement of the depression. Such erosion can be accommodated in a bottom pour vessel as shown in FIGS. 1-13 inclusive of U.S. Pat. No. 4,063,668. However, the presence of such a pocket in a vertically disposed valve, as on the sidewall of a metal processing furnace, requires consideration. For example, U.S. Pat. Nos. 4,269,399 and 4,273,315 disclose sliding gate valve arrangements that utilize a slide gate which closes the valve as the gate is moved downwardly. This has the distinct disadvantage that the erosion pocket occurs in the wall of the stationary plate and faces upwardly. The pocket, therefore, provides a receptacle in which slag or metal may collect and solidify. The solidification of this collected metal and slag not only creates abrasion of the refractory parts but can accumulate to an amount that causes the plates to be displaced from one another whereby molten metal can leak into the space created between the plates. When this occurs the valve is rendered inoperative until the refractory plates can be replaced.
Furthermore, with the valves which close in the down position, upon opening the metal cascades frgm an upper position to a lower position on the pour nozzle causing a free-fall area which initially creates a turbulence and additional errosion potential adjacent the portion of the nozzle which slides against the stationary plate. This condition can be agravated when throttling.
Accordingly it becomes desirable to develop a furnace valve which minimizes space, minimizes the potential of a pocket where slag or metal can collect in the off position, and to provide for activating the pouring with a direct connection between the furnace opening and stationary plate and the bottom portion of the pouring nozzle which communicates with either a trough or directly to a ladle.